The conventional Zerk coupler and Zerk nipple have remained virtually unchanged for well over 50 years. There are other types of couplers and nipples available on the market; however the Zerk type has become close to being the international standard.
When connecting the standard Zerk coupler to a matching nipple, the coupler is pushed against the nipple, this force displacing the retaining jaws backwards against a spring tension into a conical cavity which allows the jaws to expand over the head of the nipple. On releasing this manual force the internal spring drives the jaws forward into the tapered chamber thereby clipping the jaws over the nipple head. The angles of the taper are of such a degree that the coupler can be easily pulled off the nipple at this stage. To prevent this from happening as the grease pressure builds up, the coupler incorporates a method of exploiting the pressure in the delivery line to firmly clamp the coupler to the nipple. The higher the pressure in the delivery line, the firmer the clamping.
The negative to this scenario is that when there remains a positive pressure within the delivery line at the end of the greasing cycle it becomes very difficult to disengage the coupler from the nipple. In early versions of the Zerk coupler there was a metal to metal contact between the coupler and the nipple which was prone to by-pass and thereby relieving the pressure after greasing to allow for easy disconnection. The majority of the modern versions make use of a permanent internal seal which is a positive for reducing bypass during greasing, however has a distinct negative effect when it comes to disconnecting under pressure. In such a case the operator will need to either unscrew the coupler or agitate it vigorously relative to the nipple to encourage a bypass and allow for disconnection. In the course of such action the coupler and the nipple often become damaged and result in relatively short service life.
In searching for a more appropriate alternative the applicant has developed a grease coupler with an effective economical and easily replaceable seal and a manually operated trigger device that can be used to disconnect the grease coupler from the grease nipple even under high pressure with no twisting or manipulation. It is a requirement that the improved coupler is of a compact design to allow for access to nipples in awkward positions. Trials have shown that operator frustration is greatly reduced due to the ease of coupling and uncoupling with the nipple thereby increasing the service life of both the coupler and the nipple and in turn leads to more thorough greasing. The replaceable seal also ensures that an effective seal between the grease coupler and the nipple is achieved at all times thereby reducing waste grease at the nipple during greasing.